E.13.0 ONSITE DISPOSAL ALTERNATIVE
The Onsite Disposal alternative for Cs and Sr capsules would involve the continued operation of WESF until the disposal facility was completed. The capsules would then be removed from the basin, placed in overpack canisters, and transferred to storage for disposal where they would remain. This section analyzes potential construction, operation, and transportation risks resulting from accidents associated with this alternative.
E.13.1 CONSTRUCTION ACCIDENTS
The construction activities associated with the Onsite Disposal alternative are discussed in Appendix B of the EIS. It should be noted there are no radiological or chemical consequences associated with construction accidents. Occupational injuries, illnesses, and fatalities resulting from construction accidents are calculated in the following text.
The number of construction personnel was estimated at 2.10E+02 person-years (Jacobs 1996). The number of total recordable injuries and illnesses, lost workday cases, and fatalities for the 8 years of construction are calculated using the incidents rates from Table E.1.2.1 as follows:
Total Recordable Cases = (2.10E+02 person-years) · (9.75E+00 incidences/100 person-years) = 2.05E+01
Lost Workday Cases = (2.10E+02 person-years) · (2.45E+00 incidences/100 person-years) = 5.15E+00
Fatalities = (2.10E+02 person-years) · (3.2E-03 fatalities/100 person-years) = 6.72E-03
E.13.2 TRANSPORTATION ACCIDENTS
Transportation activities associated with this alternative include:
- Transporting construction material from offsite by truck to support WESF modifications;
- Transporting fill material from an onsite borrow site to support drywell construction;
- Transporting the overpacked capsules from WESF to drywell disposal; and
- Employees commuting to work each day.
E.13.2.1 Radiological Cancer Risk
Radiological exposures resulting from accidents during transport of the capsules to the Drywell Disposal Facility were analyzed (Green 1995), and the methodology of this analysis is discussed in Section E.1.1.6. The results of the analysis are summarized in Tables E.1 3 .2.1 and E.1 3 .2.2. The calculations show there would be no fatal cancers attributable to this exposure.
Table E.13.2.1 Integrated Radiological Impact from Accidents for the Onsite Dry Storage Alternative
E.13.2.2 Chemical Exposure
Because chemicals other than small amounts of common chemicals (e.g., lubricants) are required to implement in this alternative, essentially no chemical exposure would occur.
E.13.2.3 Occupational Fatalities and Injuries
Truck Transport
WESF would be modified to support overpacking operations. Construction material would be transported by truck from the Tri-Cities area 70 km (43 mi) away. This would require an estimated 200 trips.
The area of land that would be graded is 1.8E+03 m2 (2.2E+03 yd2). Drywells (672) would be bored with a drywell encasement placed on center in the drywell. The encasement would be backfilled with sand and covered with a sandplug after placement of the capsule in the encasement. One hundred loads of sand would be trucked from a borrow site 5 km (3 mi) away. The 672 encasement pipes would be transported by truck from the Portland or Seattle area 400 km (249 mi) away. The encasement pipe would require an estimated 14 trips.
The 1,929 capsules would be transported by truck to drywell disposal. Capsule transport would require 184 trips. Table E.13.2.3 provides a summary of the expected distance to be traveled by truck in support of the construction and capsule transport activities. The number of injuries and fatalities are calculated by multiplying the total distance traveled in each zone, shown in Table E.13.2.4 , by the appropriate unit risk factors shown in Table E.1.3.1. The expected injuries and fatalities resulting from transportation accidents associated with the alternative are summarized in Table E.13.2.5.
Table E.13.2.3 Summary of Transportation Activities for the Onsite Disposal Alternative
Table E.13.2.4 Distance Traveled in Population Zones for the Onsite Disposal Alternative
Employee Vehicles
In addition to transporting materials and supplies to and from the Hanford Site by truck, site workers and other personnel required to support the various activities will be driving to the site in their vehicles.
The total person-years to support the alternative for an estimated 88 years was calculated to be 1,294 (Jacobs 1996). Each person is assumed to work 260 days of the year. The round-trip distance traveled to work from the Tri-Cities area is estimated at 140 km (87 mi) with an estimated 1.35 passengers per vehicle (DOE 1994a). The total personnel vehicle distance was therefore calculated as follows:
(1.29E+03 person-years) · (260 days/year) · (140 km/day) · (1/1.35 person) = 3.49E+07 km (2.2E+07 mi)
The expected numbers of injuries and fatalities resulting from employee vehicle accidents were calculated as follows:
Injuries = (3.49E+07 km) · (7.14E-07 injuries/km) = 2.49E+01
Fatalities = (3.49E+07 km) · (8.98E-09 fatalities/km) = 3.13E-01
The cumulative nonradiological and nontoxicological injuries and fatalities incurred as a direct result of traffic accident impacts are summarized in Table E.13.2.6. It is most likely there would be 25 injuries and no fatalities resulting from traffic accidents.
E.13.3 OPERATION ACCIDENTS
The potential exists for accidents resulting from operation activities. The operations are discussed in Appendix B. This analysis separates and analyzes the operations according to the following modes of operation:
- Pool cell storage at WESF - Cs and Sr capsules would remain stored in water-filled basins until they are transported to drywell disposal.
- Capsule overpacking at WESF - Cs and Sr capsules would be removed from the basin and sealed in overpack canisters.
- Transport of overpacked capsules to drywell disposal.
- Storage of capsules in drywells - Cs and Sr capsules are stored in drywells for an indefinite length of time.
The potential accidents were identified in the document entitled Potential Accidents for Storage and Disposition of Cesium and Strontium Capsules for the Tank Waste Remediation System (WHC 1995k). The data package provided a range of potential accidents, probability of the accidents, and the consequences of the accidents. These accidents are summarized in the Accident Screening Table (Table E.13.3.1). The dominant accident scenarios analyzed in the following subsections were selected from the table, whose methodology was previously discussed in Section E.1.1.2.
Table E.13.3.1 Accident Screening Table for the Onsite Disposal Alternative
E.13.3.1 Pool Cell Storage Accident at the Waste Encapsulation and Storage Facility
The dominant pool cell storage accident at WESF is the earthquake previously discussed in the No Action alternative in Section E.12.2.1 and is summarized in the following.
Source-Term - The source-term presented in Section E.12.1.1 resulting from the breached canisters for the noninvolved worker receptor was 1.2E-01 Ci based on 8 hours exposure. The general public was calculated to be 3.5E-01 Ci based on 24 hours exposure. In addition to the source-term, the loss of the water shielding the capsules would result in high direct radiation doses to the receptors. It was assumed that all the workers would die in the building from the collapsed roof.
Probability - The annual exceedance frequency of the earthquake in Section E.12.2.1.2 was 2.5E-04 per year. The Onsite Disposal alternative was based on 19 years of operations; therefore, the probability was calculated to be 4.8E-03.
Radiological Consequences - The radiological consequences presented in Table E.2.2.2 are reproduced in Table E.13.3.2 .
Radiological Cancer Risk - The LCFs calculated in Section E.12.2.1.4 are the same for the Onsite Disposal alternative; however, the LCF point estimate risk is not the same due to the difference in probabilities. The LCFs and the LCF risk are calculated in Table E.13.3.3. Aside from the 10 workers dying from the collapsed roof, the calculations show there would be no fatal cancers.
Chemical Consequences - Chemical consequences presented in Section E.12.2.1.5 concluded there would be no exposure that would exceed the cumulative ratio of 1.0 to ERPG-1 values for toxic or corrosive/irritant chemicals.
Table E.13.3.2 Dose Consequence for Pool Cell Storage Accident
Table E.13.3.3 Latent Cancer Fatality Risk from Pool Cell Accident
E.13.3.2 Overpacking and Drywell Disposal Accident
Types of potential accidents associated with overpacking and drywell disposal are leaks and mechanical impacts. From Table E.13.3.1 , the DBA accident identified as having the highest risk is Accident 3.2.1, "Sr Capsule Crushed in Overpacking or Dry Storage." It was postulated that during overpacking a Sr capsule was breached when a heavy object falls on the canister.
E.13.3.2.1 Scenario and Source-Term Development for Crushed Strontium Capsule
It was assumed that the initial shock of the drop of a heavy object on the capsule would spill the entire capsule contents and loft a fraction of 1.0E-03 of the activity by free-fall. This would be resuspended for 8 hours at 4.0E-06 per hour. The source-term would be 38.5 Ci.
E.13.3.2.2 Probability of Crushed Strontium Capsule
This scenario was considered to be unlikely with a frequency range of 1.0E-02 per year to 1.0E-04 per year. For conservatism, a frequency of 1.0E-02 per year is used for calculating risk. Based on a packaging operation of 19 years, the probability was calculated to be 1.9E-01.
E.13.3.2.3 Radiological Consequence from Crushed Strontium Capsule
The radiological dose to the receptors from the accident scenario was calculated by the GENII computer code (Napier et al. 1988) using the methodology previously discussed in Section 1.1.6. The results, taken from the potential accident data package for the capsules (WHC 1995k), are summarized in Table E.13.3.4.
Table E.13.3.4 Dose Consequence from Crushed Strontium Capsule
E.13.3.2.4 Radiological Cancer Risk from Crushed Strontium Capsule
Based on a dose-to-risk conversion factor of 4.0E-04 LCF per person-rem for the worker/noninvolved worker and 5.0E-04 LCF per person-rem for the general public, the LCF risk is calculated for the receptors in Table E.13.3.5.
For the bounding scenario the calculations show there would be no fatal cancers attributable to this exposure.
The BDBA represents an unmitigated release (the HEPA filters fail). For the BDBA the calculations show all 10 workers would receive a lethal dose, there would be 1.2E+03 LCF in the noninvolved worker population, and 6.20E+02 LCFs in the general public.
E.13.3.2.5 Chemical Consequences from Crushed Strontium Capsule
Chemical consequences were not evaluated in (WHC 1995k) since the small quantity of nonradiological constituents in a capsule would result in an exposure to all receptors well below the cumulative ratio of 1.0 to ERPG-1 values for toxic corrosive/irritant chemicals.
E.13.3.3 Occupational Fatalities and Injuries
The number of operation personnel was estimated at approximately 1.08E+03 person-years (Jacobs 1996). The number of injuries, illnesses, and fatalities for the 88 years of operation are calculated as follows:
Total Recordable Cases = (1.08E+03 person-years) · (2.2E+00 incidences/100 person-years) = 2.38E+01
Lost Workday Cases = (1.08E+03 person-years) · (1.1E+00 incidences/100 person-years) = 1.19E+01
Fatalities = (1.08E+03 person-years) · (3.2E-03 fatalities/100 person-years) = 3.47E-02
TableE.13.3.5 Latent Cancer Fatality Risk from Crushed Strontium Capsule
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